The invention relates to an electric motor having a stator and a rotor, with the rotor having at least one permanent magnet and a rotor shaft being mounted radially and axially, and with the stator having at least two coils which produce a rotating magnetic field, by means of which the rotor can be driven, when alternating currents flow through them, in particular for use as a blower fan.
Motors such as these are known from the prior art, whose rotor is produced axially, by means of an axial bearing of the rotor shaft in a sintered bearing. A disadvantage of these motors is that increased wear between the sintered bearing and the rotor shaft initially causes a high level of noise emission, then leading to total failure of the motor. The object of the invention is thus to specify a motor which has a long life while at the same time producing low noise emissions.
According to the invention, this object is achieved in that the rotor is mounted by means of an elastic thrust ring, with the thrust ring being arranged axially on one side of the rotor. This axial bearing results in permanent axial bearing.
The motor can be used in any position, if a second elastic thrust ring is arranged axially on the other side of the rotor. Depending on its current position, the rotor can thus load the first or second thrust ring continuously, or the first and second thrust ring alternately. Furthermore, the elasticity of the thrust rings prevents impact noise since, when the load on the thrust rings is changed, the elastic thrust rings damp out any striking of the rotor in a sprung manner.
Elastic thrust rings which are composed of a rubber-like plastic matrix and to one side of which microfibers are applied are particularly preferable. These thrust rings have a particularly long life, since the microfibers do not become detached from the plastic matrix. If the microfibers are arranged distributed stochastically on the plastic matrix, this avoids any comb effect even when the motor rotates continuously in one direction.
The use of a lubricant in the elastic thrust ring results in even lower friction drag on the respective thrust ring, so that the rotor can reach a high rotation speed, thus floating on the elastic thrust ring and hence further reducing the wear coefficients.
A low-viscosity lubricant is particularly preferable in this case, since this results in particularly lower friction drag on the thrust rings.
If a recess is formed in the stator in order to accommodate the thrust rings, this makes it possible to reliably prevent lubricant from emerging in specific regions of the motor.
It is likewise possible to arrange one or more elastic thrust rings in a respective indentation in the rotor. A conical configuration of the recess or indentation in the stator or in the rotor, respectively, makes it possible for the lubricant which emerges from the elastic thrust ring when the latter is loaded to gather at points provided for this purpose and to be sucked up from there once again when the load is removed from the elastic thrust ring.
A stop in the stator, by means of which the axial movement of the rotor shaft can be limited when additional components are being mounted on the rotor shaft, makes it possible for the components to be pressed axially onto the rotor shaft without the elastic thrust rings being excessively compressed and hence without destroying the structures of the thrust rings and limiting the amount of lubricant forced out of the elastic thrust rings.
A capillary gap in order to accommodate lubricants sucks up lubricants which are forced out during operation and/or assembly. When the load on the thrust ring is removed, the thrust ring can absorb the lubricant once again, due to the capillary effect.
Particularly simple radial bearing can be achieved by the rotor shaft being polished in the region of the radial bearing points.
The rotor can be produced particularly easily if the permanent magnet is embedded in plastic.
The motor can be designed to be particularly compact if the stator is designed as a winding body with coils which are fit on it, and if the rotor is arranged inside the winding body.
The abovementioned physical form can be produced particularly easily if two crossing coils are fit on the winding body.
If there is a phase separation between the alternating currents in the individual coils which corresponds to the angle of orientation of the individual coils to one another, the motor efficiency is high.
If the alternating currents are additionally sinusoidal, this results in the motor running particularly quietly, with little vibration.
Its quiet running characteristics mean that the motor described above is particularly suitable for operation as a fan motor with a fan impeller mounted on the rotor shaft.